The object of this work was the self-passivated Ti-15 wt % Mo implant alloy subjected to anodic oxidation in 1 M acetic acid aqueous solution at 5 V for
1 h. In order to thicken the oxide film a superior biocompatibility and corrosion resistance of the anodized implant was achieved. Surface of the tested alloy
before and after anodizing was characterized using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy dispersive X-ray
spectroscopy (EDS) and profilometry. Electrochemical impedance spectroscopy (EIS) measurements revealed a passive behaviour of the alloy under the
experimental conditions. The bilayer oxide film consists of a porous outer layer (6.7&#177;1.0 nm) and a thin, solid inner-barrier layer (1.4&#177;0.3 nm). The obtained
film is three times thicker than the oxide layer formed by self-passivation. The electrochemical studies in physiological saline solution (PSS) at 37°C showed
that the anodic oxidation improved the corrosion resistance of the Ti15Mo alloy. No pitting corrosion was detected in anodic polarization measurements up
to 9.5 V due to the presence of the barrier oxide layer on the alloy surface and phase composition of the examined alloy which contained only &#946;-Ti phase.
Key words: Ti15Mo alloy, anodization, oxide layer, corrosion resistance, EIS.1. INTRODUCTION
In recent years titanium and its alloys were found to be very popular
biomaterials for medical applications due to their excellent mechanical
properties, high biocompatibility and good corrosion resistance
[1]. Nowadays, toxic metals present in medical titanium alloy are
replaced by neutral and non-harmful ones for human body. Among
these materials, Ti15Mo alloys can be some examples. Allergenic
and carcinogenic elements such as Ni, Al and V have been replaced
by a biocompatible molybdenum [2]. Addition of Mo increases the
corrosion resistance simultaneously reducing the elastic modulus
[3]. If the Mo content is higher than 10...
»

Nitriding is commonly used method of thermochemical treatment in order to produce surface layers of improved hardness and wear resistance. Using a gas
nitriding with changeable nitriding potential, a nitrogen concentration at the surface could be controlled, influencing the phase composition and the growth
kinetics of the layer. In this study, the hybrid surface treatment was applied. It consisted in gas nitriding and laser heat treatment (LHT) of 42CrMo4 steel.
Two nitriding processes were carried out using changeable nitriding potential. Parameters on first process were as follows: temperature 570°C (843 K), time
4 h. The second process was performed at lower temperature 520°C (793 K) and longer duration 10 h. This resulted in various depths of the compound zone
at the surface (20 and 8 &#956;m, respectively). Next, the nitrided layers were laser heat-treated using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were
arranged as the single tracks with various scanning rates (vl = 2.88 m/min and vl = 3.84 m/min). The laser beam power (P) ranged from 0.26 to 0.91 kW.
The effects of the depth of compound zone as well as LHT parameters on the microstructure, dimensions and microhardness of laser tracks were analysed.
In the majority of the produced laser tracks, remelted (MZ) and heat-affected (HAZ) zones were easily identified. Different microstructure was visible at
low laser beam power (0.26 kW). The dimensions of MZ were limited, whereas the HAZ was clearly observed. The compound zone was still visible at the
surface. Only the porous &#949; nitrides were slightly melted. Hardness increased significantly after LHT with complete and partial remelting of compound zone.
Laser beam power and scanning rate influenced the depth and width of MZ and HAZ, so the thickness of hardened zone. The greater laser beam power or
the smaller scanning rate, the larger hardened zone was observed.
Key words: gas nitriding, laser heat treatment, microstructure, hard...
»

The work presents research results of impact of Nb, Ti and V microadditions on recrystallization kinetics and microstructure of newly elaborated steels
assigned for production of forged machine parts, using the method of thermomechanical treatment. The study was performed with the use of Gleeble 3800
simulator. In order to determine recrystallization kinetics of plastically deformed austenite, discontinuous compression tests of specimens were done with
a given strain at the rate of 10 s-1, in a temperature range from 900 to 1100°C, with isothermal holding of samples between successive stages of deformation
for 2 to 100 s. Recrystallization kinetics of plastically deformed austenite was described using the Johnson-Mehl-Avrami equation. Performed two-stages
compression tests revealed that microadditions introduced into steel considerably influence the kinetics of static recrystallization. Determined time of total
recrystallization of austenite, tR, in a temperature range from 1100°C to 900°C changes from 100 to 600 s and from 300 to 800 s &#8212; for the Ti-V steel and
Ti-Nb-V steel, respectively. Executed hot compression tests will contribute to establishing conditions of forging with the method of thermomechanical
treatment.
Key words: HSLA steels, thermomechanical treatment, static recrystallization.1. INTRODUCTION
HSLA-type (High Strength Low Alloy) microalloyed steels &#8212; containing
up to 0.3% C and 2% Mn and microadditions with high
chemical affinity to N and C, i.e. Nb, Ti and V in the amount of
about 0.1%, and sometimes also slightly increased concentration of
N and up to 0.005% of B, increasing hardenability &#8212; are particularly
useful for production of forged parts with fine-grained microstructure
using the method of thermomechanical processing. The
interaction of microadditions in steel in a solid state depends on their
state under conditions of performed plastic working. Microadditions
dissolved in a solid solution rais...
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TiO2 coatings on 316L steel were obtained by use of electrophoretic deposition (EPD) method. Potential zeta of nc-TiO2 particles in suspensions containing
water and ethanol in different ratios was measured. Suspensions&#8217; pH was stabilized by addition of acetic or citric acid and ammonia solution. Addition of
citric acid in small amount decreased the zeta potential. Optimal suspensions&#8217; parameters for cathodophoretic and anodophoretic deposition were selected
based on the results of zeta potential measurements versus pH for suspensions with different water-ethanol concentration. For the chosen suspensions the
rate of TiO2 deposition was measured. Coatings&#8217; cohesion was improved by sintering or addition of biopolymer (chitosan) into suspension. The microstructure
of coatings was examined by scanning electron microscopy. The roughness and thickness of the coatings were measured by optical profilometer.
The corrosion resistance in Ringer&#8217;s solution was examined by use of polarization curves. The corrosion resistance of coated steel was higher than that of
uncoated one. For sintered coatings the corrosion currents were lower, but the passive area was larger for not sintered ones. The contact angle of the coatings
was measured using a sitting drop method and superhydrophilic properties of TiO2 coatings were confirmed. Manufactured coatings may be potentially used
as self-cleaning materials. Additionally, TiO2 coatings improve corrosion resistance of steel and exhibit good bactericidal properties. These characteristics
may make this sort of materials potentially useful also for medical purposes.
Key words: TiO2 coatings, electrophoretic deposition, 316L steel, zeta potential measurements, superhydrophilic coating.1. INTRODUCTION
Stainless steel is commonly used in many areas, e.g. marine systems,
nuclear, chemical, food, construction industries and biomedical
purposes [1÷3]. A wide range of industrial applications is possible
...
»

The freestanding Ti/Al multilayer (with 3:1 the chemical composition ratio) was applied to bond the parts from Ti-6Al-4V alloy. The as-deposited multilayer
and the joint obtained with it were characterized with the use of transmission electron microscopy (TEM) method including selected area electron
diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS). It was observed that the annealing at 800°C for 1 h in vacuum of 1 Pa helped to
transform Ti/Al multilayer into fine grains (grain size < 1 &#956;m) of Ti3Al acting as a filler material between pieces of Ti-6Al-4V. The resulting joint shows
generally good connection with the presence of small porosity both at the filler material/Ti-6Al-4V base material interface (larger) and on the Ti-6Al-4V
side (smaller). Additionally, near surface zone of the joint, the parts were strongly depleted of aluminium.
Key words: diffusion bonding, Ti/Al multilayers, Ti-6Al-4V alloys, TEM, EDS.1. INTRODUCTION
Heating of Ti/Al multilayers could result in the formation of various
titanium aluminides, such as Al3Ti, Ti3Al or TiAl. Due to negative
enthalpy of mixing their formation is accompanied by a strong exothermic
effect [1, 2].
The type of a final product depends on the bilayer thickness ratio,
i.e. averaged multilayer chemical composition. However, slow
heating of the whole multilayer causes that the reaction is controlled
through a solid state diffusion (SSD) across neighboring interfaces
being an example of one of phase transformations in solid state [3].
The level and extent of the local intermixing, both increasing with
lowering of the multilayer period, decides on the phase precipitation
sequence taking place during this process [4]. Fast local temperature
rise leads to a reaction known as self-propagating hightemperature
synthesis (SHS) occurring along the multilayers in the
form of roughly planar front. In Ti/Al multilayers it is accompanied
by melting of aluminium layers and conseque...
»

The HR6W alloy (23Cr40Ni30Fe7WTiNb) is a candidate for boiler components of advanced ultra-supercricical (A-USC) conventional power plants. The
influence of isothermal ageing at 700°C and 900°C for up to 110 hours on the microstructure of HR6W alloy was investigated in detail by advanced scanning
and transmission electron microscopy methods. The results show that, beside primary MX carbonitrides, the M23C6 and Laves phase, Fe2W, were
precipitated in the austenitic matrix. Their size and spatial distribution depend on ageing conditions. Microstructure changes influenced the hardness of the
investigated alloy.
Key words: HR6W, microstructure, scanning electron microscopy (SEM), transmission electron microscopy (TEM), steam power plant (SPP).1. INTRODUCTION
The HR6W is Ni-Fe based alloy produced by Nippon Steel &
Sumitomo Metal Corporation with a nominal composition of
23Cr40Ni30Fe7WTiNb designed for tubing, especially for superheaters
and reheaters coils and for thick-walled elements of boilers.
The HR6W alloy is the candidate for advanced ultra-supercritical
(A-USC) boiler pressure elements owing to its superior creep and
oxidation resistance at high temperature [1÷4].
The aim of the study was to examine a stability of the HR6W
alloy microstructure during ageing at 700°C and 900°C affecting
its mechanical properties during service in the power plant. The
highest ageing temperature was chosen based on phase equilibrium
diagrams and corresponds to operating temperature of 670°C for up
to 200 000 hours service for HR6W alloy [5].
2. MATERIAL AND EXPERIMENTAL DETAILS
The chemical composition of the investigated HR6W alloy and
standard requirements for HR6W alloy are presented in the Table 1.
The alloy was delivered as the tube with outside diameter of
38 mm and wall thickness of 8.8 mm. The as-received alloy was
solution treated at temperature range of 1190÷1250°C followed by
fast cooling [6]; the exact parameters of heat treatment were...
»

Metal spinning is a forming process known since ancient times. However on an industrial scale it is used from the beginning of the twentieth century. Thanks
to the technology it is possible to obtain complex axisymmetric shapes with excellent mechanical and surface properties. It is a promising forming technology
that is becoming more popular especially in advanced application such as aircraft industry. It has a lot of advantages; among others it allows shaping the
material properties in a larger extent than the commonly used metalworking methods. Furthermore since 2001 for the first time laser assisted heating was
used in the process enhancing it even further. The article presents the metal spinning technology and its current developments. Additional practical aspects
were described in the research and underlined by the authors. The last paragraph concerns sample results of mechanical tests carried out on the fabricated
elements that show the possible application of the method particularly in the aircraft industry. The hardness of the cold formed element increased more than
twice after 70% reduction in cross section in a single tool movement. In the longer term perspective laser assisted metal spinning could reduce the costs and
improve the properties of the currently used aircraft engine parts by eliminating intermediate annealing.
Key words: metal spinning, shear forming, aircraft materials, Inconel 625.1. INTRODUCTION
The process for metal spinning has been known since ancient times.
In its kinetics, the process is derived from craft techniques used in
pottery. The rotary element is formed by the pressure of the tool
(rollers) rotating around its own axis, reproducing the final shape of
the product on the mandrels (rotating form). Processing is continuous;
its advantage is the possibility of forming complex axisymmetric
shapes. Additionally, a large number of control parameters allow
for a wide scope in controlling not only the dimensi...
»

Increase of the coal fired power plants efficiency is inseparable with an increase of the steam conditions. Currently used 9÷12% Cr steels are not able to
withstand pressure of 30 MPa at 700°C for a long time due to their microstructure instability leading to fast damage. Development of new Fe-based materials
able to work under advanced ultra-supercritical (A-USC) conditions for a long time is the key of importance. Present paper deals with a microstructure of
the prospective, 22% Cr austenitic steel, Sanicro 25, heat treated or oxidized in water vapour at 700°C. Detailed characterization of the steel was performed
using X-ray diffractometry as well as scanning and transmission electron microscopy techniques. Investigation led to establish the effect of temperature and
water vapour environment on the microstructure stability of this modern austenitic steel. The results showed that the microstructure of the aged steel consists
of M23C6 and Laves phase precipitated on the grain boundaries as well as &#949;-Cu, NbN, M23C6 and Z-phase precipitated within the grains. After oxidation at
700°C up to 5000 h in water vapour, Sanicro 25 developed a thin protective oxide scale at the surface, consisting mainly of Cr2O3 plates, characteristic for
steels oxidation in vapour.
Key words: Sanicro 25, TEM, oxidation, water vapour, A-USC.1. INTRODUCTION
Nowadays, environmental protection takes a particular significance
due to high emission of CO2, which is one of the major greenhouse
gases causing global warming. Major CO2 sources are coal-fired
power plants, therefore particular efforts are made in order to decrease
the CO2 emission by increasing the thermal efficiency of
the power plants due to enhancing temperature and pressure of the
steam to 700°C and 30 MPa, respectively. Such change, however,
has strong impact on the microstructure stability and lifetime of the
currently used materials. Commonly used 9÷12% Cr steels are not
suitable to operate at t...
»

In this work the thermal stability of silicon-doped diamond-like carbon (DLC) films was investigated. The studied coatings were produced by radio-frequency
plasma assisted chemical vapour deposition (RF-PACVD) method with use of tetramethylsilane (TMS) as a silicon precursor. As-deposited Si-DLC
coatings with three different silicon concentrations were annealed at 400°C, 500°C, and 600°C for 1 hour in air atmosphere. For comparison DLC coatings
were also examined. It has been shown that the level of disorder of Si-DLC increases with the increase of silicon concentration. Silicon admixture improves
the thermal stability of Si-DLC coatings by slowing down and delaying the graphitization processes compared to the undoped DLC films. Furthermore, an
increase in hardness of the Si-DLC coatings annealed at the temperature of 400°C has been observed. The DLC and Si-DLC coatings with the lowest Si
concentration annealed at 500°C, and all of the coatings annealed at 600°C have been completely degraded. The coatings with the highest concentration of
silicon that have stood the annealing process at 500°C have demonstrated a high degree of graphitization and degradation, manifesting itself in the lowest
mechanical properties and a significant reduction in their thickness.
Key words: thermal stability, silicon doping, DLC films.1. INTRODUCTION
Diamond-like carbon (DLC) films are characterized by many
unique properties. These include high biocompatibility [1], high
hardness [2], low coefficient of friction, [3, 4] good anti-wear [4]
and anti-corrosion [5] characteristics. Hence, these films are commonly
used as protective coatings in automotive industry, magnetic
data storage, machining tools and biomedical applications [1÷3,
6]. However, DLC coatings have several known disadvantages.
One of them, severely limiting their large scale application possibilities
is the low thermal stability at high working temperature.
It has been reported that DLC coating...
»

A high temperature exposure of nickel-base single crystal superalloys leads to a formation of topologically close packed (TCP) phases, what can deteriorate
their creep strength. Therefore, the aim of the present work was to investigate TCP phases precipitated in CMSX-4 superalloy after a two-step treatment consisting
of annealing at temperature of 1100°C followed by a creep deformation at temperature of 900°C. The microstructure of CMSX-4 superalloy exposed
to a high temperature was investigated by means of scanning and transmission electron microscopy as well as scanning-transmission electron microscopy
in high angle annular dark field mode. The chemical composition in nanoareas was determined using the high spatial resolution and high count rate energy
dispersive X-ray spectroscopy. A three-dimensional characterization of the microstructure of annealed and creep tested single crystal superalloy was carried
out by means of electron tomography. Results of microstructural investigation have shown that after the application of two-step high temperature exposure the
TCP precipitates present in CMSX-4 superalloy are P and &#956; phases. The most pronounced differences in the chemical composition of the investigated P and &#956;
phase particles are concerned with W and Re content. It was determined that the P phase contains a higher amount of W, while the &#956; phase is mostly rich in Re.
Key words: single crystal nickel-base superalloys, annealing, creep, TCP phases.1. INTRODUCTION
Single crystal nickel-base superalloys are especially designed for
gas turbine blade and vane applications. The microstructure of single
crystal superalloys consists of two phases, namely the &#947; phase
matrix and cuboidal &#947;&#697; phase precipitates. To increase the high temperature
creep resistance of single crystal superalloys, high amounts
of refractory elements such as Mo, W and Re are added. These elements
provide a solid solution strengthening, but unfo...
»

The aim of the present work was to investigate the influence of polyethylenimine, a cationic polymer surfactant, on the microstructure and corrosion resistance
of SiO2 and Ni/SiO2 coatings electrophoretically deposited on 316L stainless steel. The relationship between zeta potential and pH of the ethanol-based
suspensions of SiO2 and Ni powder particles with addition of polyethylenimine was determined. The parameters of electrophoretic deposition process
(applied voltage, time, distance between electrodes) were developed to prepare good quality coatings. Cathodophoresis from suspensions with polyethylenimine
addition was performed with slightly lower applied voltage and time as compared to anodic deposition of coatings without surfactant. The microstructure
of the coatings, their surface roughness and adhesion to the substrate were investigated. The protective behaviour of the coatings was studied by
potentiodynamic measurements in 3.5% NaCl water solution. The microstructure and properties of the coatings were compared with those obtained without
polyethylenimine addition. It was determined that the microstructure of SiO2 and Ni/SiO2 coatings deposited from suspensions containing polyethylenimine
was more uniform and contained smaller amount of cracks and voids than the coatings achieved without polyelectrolyte. It was also observed that the quality
improvement of the coatings deposited on 316L steel due to addition of polyelectrolyte with binding properties leads to increase of their corrosion resistance.
Key words: electrophoretic deposition (EPD), SiO2 coatings, Ni/SiO2 composite coatings, polyelectrolyte, polyethylenimine.1. INTRODUCTION
316L stainless steel is widely used in applications involving severe
corrosive conditions. Due to the formation of a thin chromium oxide
film the steel exhibits good corrosion resistance in oxidising
media [1]. However, in Cl- containing environment, deterioration
of the passive film occurs and the stee...
»

Fatigue damage process developing in structural materials under long-term cyclic loading is still an unsolved problem of modern engineering. Attempts to
assess a degree of materials degradation under fatigue conditions on the basis of changes in the areas of local strain concentration determined by optical
methods can be treated as the promising contemporary research direction of majority of scientific centres in the world. In most cases, fatigue damage has
a local character and it is based on damage development leading to generation of cracks appearing around structural defects or geometrical notches. An
identification of these areas and their subsequent monitoring requires a full-field displacement measurements performed on the objects surfaces. It seems
that modern contemporary optical methods for displacement components measuring on the surfaces of structural elements or tested specimens are suitable
for such purpose. Digital Image Correlation (DIC) and Electronic Speckle Pattern Interferometry (ESPI) are nowadays the most widely used testing methods
in this area. Both of them enable capturing of displacement and strain components distributions. This paper presents an attempt to use the ESPI method for
fatigue damage evaluation and its monitoring on specimens made of the aluminide coated nickel super-alloys. Flat specimens were subjected to cyclic loading.
The fatigue tests were interrupted several times in order to perform a static loading during which the optical measurements were carried out. An analysis
of the results captured by the ESPI system allowed indication of places of the greatest stress concentration and demonstration of the damage development
process as a function of the increasing number of cycles.
Key words: fatigue, damage, super-alloy, Electronic Speckle Pattern Interferometry.1. INTRODUCTION
Experimental assessment of damage development in materials subjected
to cyclic loading requires continuous monitoring of the disp...
»

The direct laser interference lithography, based on bi-prism, tetragonal pyramid and an axicon was used as a tool for periodical structuring of different bioscaffolds.
The simple, source laser system with stable Nd:YAG laser resonator, amplifying system (energy up to 1 J) and prism-based interferometer optics
gave possibility to create periodical, linear, dotted and even circular surface structures, with high degree of periods, width and depth control. The general
idea consists of the imitation of the structure and function of tissues and adoption of these solutions for the material science. It is well known that the influence
of the artificial material on the cellular processes related to the differentiation, proliferation and growth are dependent on the chemical composition and
surface topography as well as mechanical properties of applied materials. The most recent studies focus on the cell interaction with flat scaffolds. However,
cells are found covering a highly rough surface in the blood vessels. The work was related to reconstruction of the structure and function and topography of
luminal side of the blood vessels. The most important aspect was to recreate cellular niches which plays specific function on the activation and differentiation
of stem cells. The mechanical stresses generated at any certain site depend on the surface micropatterns of the material as well as the other signals that cell
receives from chemical stimuli. This work is one of the first attempts to determine correlation of surface micro-topography with biochemical stimulation by
adsorbed on the materials surface molecules and both factors potential influence on cellular response. The study was aimed at showing the mechanism of
human endothelial progenitor cells adhesion, morphology and function control in response to surface patterning. It was found that micro-channels enhanced
intercellular connections forming tight junctions and the appropriate progenitor cell diff...
»

This paper presents results of manufacturing the ceramic porous granules made of the local waste materials. These granules were produced from the mixture
of the car wind-shield glass contaminated by residuals of the PVB foil and aluminosilicate-based mine slates. Addition of the leather tanning wastes was
used in order to increase granules porosity without significant decrease of mechanical properties. The paper shows the effect of tanning wastes addition
and sintering parameters on the properties of the resultant granules in comparison to the leather-free product. Porosity, apparent density and water absorption
were examined according to EN 1097 standard, and compressive strength was examined according to UNE-EN 13055-1 standard. Differences in the
microstructure of granules were examined using scanning electron microscope. Partial substitution of both starting materials by tanning wastes and/or the
two-step sintering regime could significantly improve the physical properties, what has been shown in the present paper.
Key words: ceramic granules, leather tanning waste, recycling, waste management, windshield glass.
Inżynieria Materiałowa 3 (211) (2016) 131÷136
DOI 10.15199/28.2016.3.7
&#169; Copyright SIGMA-NOT MATERIALS ENGINEERING
1. INTRODUCTION
Nowadays, there are several issues related to recycling the car
windshield glass. One of these problem is related to the layered
structure of a car windshield. Two layers of glass are separated
by a polymer layer of polyvinyl butyral (mainly known as PVB),
which improves mechanical properties of the laminated material
but simultaneously it prevents the separation of layers in the waste
glass during a mechanical treatment. Advanced technology allows
to separate those layers during screening resulting in separation of
PVB as a large-sized fraction from the fine glass powder. It is impossible
to produce the windshields again from these materials, but
the PVB scraps can be used once more as an...
»

The aim of this work was to indicate the influence of changes on the surface of materials caused by the corrosive medium (3.5% NaCl solution) on the intensity
and character of the Portevin-Le Chatelier effect in model aluminium alloys. For this purpose, two Al alloys, containing 1% and 3% of magnesium,
were subjected to tensile testing in the as-cast state and after the exposition in NaCl solution for various time. Several electrochemical measurements were
held to determine materials&#8217; corrosive behaviour and microscopic observations to evaluate the surface character of the samples. High corrosion resistance
of the materials resulted in a very slight alteration of their surface development, which didn&#8217;t lead into any significant variations in the plastic instability
phenomenon PLC.
Key words: Portevin-Le Chatelier effect, aluminium alloys, plastic instability, corrosion.
1. INTRODUCTION
Portevin-Le Chatelier effect (PLC effect) is a well-known phenomenon
occurring in many aluminium alloys during deformation
[1], manifesting itself in a form of characteristic serrations on the
stress-strain curve, caused by rapid changes of force in small extensions.
It can lead to inhomogeneous deformations in materials microstructure,
resulting in the deterioration of its mechanical properties
[2]. Apart from the most commonly analysed structural factors,
like grain size, precipitations or texture, there are some extrinsic
ones which can also strongly influence materials vulnerability to
PLC effect [3].
Abduluyahed in his research [4, 5] compared serrated flow in
316 and 316L austenitic steels during tensile testing in air and in
vacuum. He reported a considerable decrease in serration frequency
in vacuum conditions, which can be subjected to the fact that
there is no oxygen layer on the surface, which could crack during
deformation and work as a stress concentration. Temperature was
considered as a factor influencing PLC effect, by Yilm...
»

This paper is showing the results of study devoted to determination of the chemical composition and strengthening process parameters effect on the precipitation
sequence of intermetallic phases in the supersaturated 2xxx aluminium alloys. This study was based on a calorimetric study where temperature&#8217;s effects
were determined when precipitation process occurred during heating with different heating rate of the supersaturated alloys group of 2xxx. Based on the calorimetric
curves and estimated values of ln(Q/T2) and 1000/RT an activation energy for precipitation and dissolution of phase components were evaluated.
Key words: aluminium alloys, precipitation strengthening, calorimetry, activation energy.
Inżynieria Materiałowa 3 (211) (2016) 104÷108
DOI 10.15199/28.2016.3.2
&#169; Copyright SIGMA-NOT MATERIALS ENGINEERING
1. INTRODUCTION
The 2xxx series of aluminium alloys generally contain 2 up to 10%
copper, with smaller additions of other elements. The copper provides
substantial increases in strength and facilitates precipitation
hardening. The introduction of copper to aluminum can also reduce
ductility and corrosion resistance [1, 2]. Thus, the most common
applications for these type of alloys are aerospace and automotive
industries. Due to both the development of new alloys, as well as
the constantly increasing demands on their performance, there was
a still need to examine the effect of chemical composition, kinetic
of precipitation processes from supersaturated solutions and the influence
of strengthening phases on the final mechanical properties
of newly developed aluminium alloys. The mechanism of age hardening
responsible for strengthening is based on the formation of intermetallic
products through the decomposition of a metastable supersaturated
solid solution SSS obtained by solution treatment and
quenching. Since the interactions between the decomposition products
and the dislocations are mainly responsible for the...
»

The use of fillers in the production of plastic products is intended to improve their properties, the wider use and reduce prices. The ageing of polymers
results in deterioration of strength properties of the material. Forecasting changes caused due to ageing allows to determine the feasibility of application of
the composites under certain conditions. The article presents the results of investigations of polyethylene (Hostalen 7260, Lyondellbasell) with cardboard
and dye composites before and after electrochemical ageing. Ageing process was performed in special chamber, in water solution of NaCl (35&#8240;) at pH 7 and
at 20°C for 720 h (current 0.3 A). Samples with the addition of 2% dye, 2% dye and 2% cardboard, 2% dye and 4% cardboard, 2% dye and 6% cardboard
were tested. The carboard filler was made by mechanical fragmentation. The samples were injected using a KraussMaffei KM65-160C1 injection moulding
machine. Tensile strength was measured. The thermal properties were analysed using a DSC method. Structure was observed using light microscope. Hardness
was determined with ball pressing method. The aim of the investigations was to determine the influence of the filler on the composite properties and to
receive a new, cheaper material. Changes in the degree of crystallinity, the melting point range, structure of the tested materials were revealed. The changes
in mechanical properties of polyethylene with filler and dye before and after ageing were observed. The studies show that the electrochemical ageing causes
significant changes in the properties of the tested materials
Key words: polyethylene, composites, dye, cardboard, structure, thermomechanical properties.
Inżynieria Materiałowa 3 (211) (2016) 120÷125
DOI 10.15199/28.2016.3.5
&#169; Copyright SIGMA-NOT MATERIALS ENGINEERING
1. INTRODUCTION
Polymeric composites are manufactured using the three methods:
physical, chemical and physical-chemical. The physical method is
the most po...
»

The effect of porosity on microstructure and thermal properties of titanium diboride (TiB2) based cermets with Cu binder was investigated. It has been demonstrated
a good wettability of the TiB2-Cu interfaces which allows for heat flow through it easily but formed microporosity (25÷32 %) and related structural
defects in the sintered cermets affects the thermal conductivity. The specific heat changes exponentially with temperature and amounts to 0.37 J&#8729;g-1K-1 at
298 K for the TiB2-Cu (20 vol. %) cermet with the lowest porosity. The X-ray diffraction (XRD) analysis confirmed that TiB2-Cu is the stable system and
there was no reaction between TiB2 and Cu. The dependence of microstructure and composition on thermal properties of sintered the TiB2-Cu cermet alloys
was discussed.
Key words: titanium diboride, TiB2-Cu cermets, ceramic matrix composites (CMCs), hot isostatic pressing, HIP, thermal properties.
Inżynieria Materiałowa 3 (211) (2016) 109÷114
DOI 10.15199/28.2016.3.3
1. INTRODUCTION
Titanium diboride (TiB2) is one of a few refractory metal borides
with an attractive combination of properties such as high melting
point (3225°C), ultra-high hardness (25 GPa), high strength to density
ratio, good thermal and electrical conductivity (96 W&#8729;m-1K-1 and
22&#8729;106 Wcm, respectively) and wear resistance [1, 2]. TiB2 can be
used to produce dense constructive sintered materials for high-temperature
structural applications as well as for control rod elements
with a high-thermal neutron absorption in nuclear reactors. However,
it is well known, that wide applications of TiB2 ceramic are limited
due to poor sintering ability, which requires extremely high temperature
[3, 4]. The interesting approach for obtaining the TiB2 based cermets
is the sintering method by hot isostatic pressing (HIP). In this
way by intensive mass transfer the sintering process is carried out in
shorter time and at lower temperature. The lower temperatu...
»

Among the precipitation hardening stainless steels, martensitic grade of 17-4 PH has a special importance. This steel exhibits a good combination of high
mechanical properties and good corrosion resistance. Therefore it is widely used in many branches of industry. The pitting corrosion behaviour of sintered
17-4 PH steel processed under different aging processing conditions in 0.5 M NaCl solution at 25°C was studied by open circuit potential measurement and
potentiodynamic polarization technique. Compared with the sintered 17-4 PH, the corrosion resistance of the solution treated and aged steels were improved,
as evidenced by a noble shift in open circuit potential, a higher pitting potential, a higher polarization resistance and a lower passive current density. Considering
the influence of aging temperature on the pitting behavior of the 17-4 PH steel, it can be concluded that steel aged at 480°C exhibited the highest
corrosion resistance in 0.5 M NaCl solution. While aging treatment at 500°C resulted in the worst corrosion resistance. In addition, the hardness of the solution
treated and aged 17-4 PH was higher than that of the sintered steel.
Key words: 17-4 PH stainless steel, pitting corrosion, hardness.1. INTRODUCTION
It is known that the corrosion destruction is one of the main sources
of material loss. And furthermore it contributes to the pollution of
the environment and even constitutes a risk to human health. The
problem of materials durability in natural and artificial environments
is extremely important from the viewpoint of design and also
application of constructions, devices, tools and etc.
The degradation of the materials and the environment as a result
of corrosion can be effectively reduced by appropriate prevention,
mainly by using methods of anticorrosive protection and adequate
selection of materials.
The steels containing at least 10.5 wt % chromium and other elements
(such as nickel or molybdenum) are more resist...
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Good resistance to corrosion and oxidation of austenitic 316L steel is well-known. Therefore, this material is often used wherever corrosive media or high
temperature are to be expected. However, under conditions of appreciable mechanical wear (adhesive or abrasive), this steel have to characterize by suitable
wear protection. The diffusion boronizing can improve the tribological properties of 316L steel. However, the small thickness of diffusion layer causes
the limited applications of such a treatment. In this study, instead of diffusion process, the laser boriding was used. The external cylindrical surface of base
material was coated by paste including amorphous boron and CaF2 as a self-lubricating addition. Then the surface was remelted by laser beam. TRUMPF
TLF 2600 Turbo CO2 laser was used for laser alloying. The microstructure of remelted zone consisted of hard ceramic phases (iron, chromium and nickel
borides) located in soft austenite. The layer was uniform in respect of the thickness because of the high overlapping used during the laser treatment (86%).
The obtained composite layer was significantly thicker than that-obtained in case of diffusion boriding. The remelted zone was characterized by higher hardness
in comparison with the base material. The significant increase in wear resistance of laser-borided layer was observed in comparison with 316L austenitic
steel which was laser-alloyed without CaF2.
Key words: laser boriding, self-lubricating addition, microstructure, hardness, wear resistance.1. INTRODUCTION
AISI 316L austenitic stainless steel is well-known for its good corrosion
resistance as well as good resistance to high temperature.
It results from a single-phase austenitic microstructure as well as
from an effective balance of carbon, chromium, nickel and molybdenum
content. Therefore, this steel is often used wherever a high
temperature or aggressive corrosive media occur. However, this
material is characterized by l...
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Ni-based superalloys are often used in many industrial applications, for example in chemical, petrochemical, aeronautics, nuclear or space industries. These
alloys are characterized by a unique combination of low thermal expansion coefficient, high temperature strength, high resistance to oxidation and high corrosion
resistance. However, due to their low microhardness and sensitivity to abrasive, erosive and adhesive wear, their application is limited. The boriding
process is the appropriate treatment, which will provide high hardness and high wear resistance of Ni-based alloys. Unfortunately, the use of boride layers
is limited by their sensibility to cracking under mechanical stresses. Therefore, in this paper the microstructure, microhardness and fracture toughness of
gas-borided layer produced on Nimonic 80A alloy were studied. Gas boriding in N2-H2-BCl3 atmosphere was proposed to produce the hard boride layer on
Nimonic 80A alloy. This process was carried out at 920°C (1193 K) for 2 hours. The carrier gas consisted of 75 vol.% N2 and 25 vol.% H2. Proposed gas
boriding accelerated the diffusion of boron into the surface in comparison with other acceptable diffusion methods. The comparable thickness of boride layer
was obtained after considerably shorter duration.
Key words: gas boriding, Nimonic 80A alloy, microstructure, hardness, fracture toughness.1. INTRODUCTION
Nickel-base superalloys are generally used for application under
conditions of high stresses in high temperature, because of their
excellent combination of oxidation resistance, corrosion resistance,
good stress relaxation resistance and good mechanical properties
even at high temperature [1÷3]. However, because of poor wear
resistance, the Ni-base alloys under condition of mechanical wear
(abrasive or adhesive), require suitable and effective protection.
Boronizing is a surface treatment that increases the hardness and
wear resistance of metals and their alloys. Generally...
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Many researchers nowadays concentrate on nanocrystalline metal-matrix composites, as well as on composites reinforced by nanoparticles, to find more
suited materials to be used in aviation, nuclear power plants or as a hydrogen storage for fuel cells. The aim of this paper was to investigate the possibility
of producing nanocrystalline nickel-based composite coatings reinforced by carbon nanotubes (Ni-CNT). The goal was to obtain well immersed carbon
nanotubes fully dispersed in nanocrystalline nickel matrix by using standard electrochemical deposition equipment and modify the process by changing
parameters like bath composition, additives, nanotubes content or stirring method. The effect of optimization of these parameters on composite&#8217;s microstructure,
surface topography and nanohardness was investigated. Also, usefulness of different approach, so called &#8220;stirring electrode" was examined. Scanning
electron microscopy, transmission electron microscopy with electron diffraction, X-ray diffraction and Raman spectroscopy were used to determine the
microstructure of obtained coatings.
Key words: nickel nanocomposite, carbon nanotubes, metal-matrix composite, microstructure, nanohardness.1. INTRODUCTION
Many researchers are now focusing on the development of the composites
with nanocrystalline metal matrix and composites reinforced
by the nanoparticles [1÷3]. Since the discovery of carbon nanotubes
[4] an intensive work has been done in attempt to exploit their properties,
and tries has been made to include them as a reinforcement
of nanocomposites [5÷7]. Composites like that are used in aerospace,
nuclear energy and as the storage of hydrogen in fuel cells
[5]. An example of such a material is a nanocrystalline nickel matrix
based nanocomposite reinforced by carbon nanotubes (Ni/CNTs).
They are currently attempts to produce this type of material in the
form of geometric solids with significant volumes, such as a few
millimeters...
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The influence of two variants of initial soaking at 1100°C/2 h and 1150°C/2 h and parameters of hot plastic deformation on the deformability of Fe-Ni
superalloy have been presented. The hot deformation characteristics of alloy were investigated by hot torsion tests using Setaram torsion plastometer. The
tests were executed at constant strain rates of 0.1 and 1.0 s-1, and testing temperature in the range of 900 to 1150°C and were conducted until total fracture
of the samples. Plastic properties of the alloy were characterized by worked out flow curves and the temperature relationships of maximum yield stresses
(&#963;pp) and strain limits (&#949;f). The flow stress of the torsion tests showed a single peak in the flow stress-strain curves, and indicated that a dynamic recovery
and recrystallization took place during the hot deformation. It was found that optimal values of flow stresses and strain limits were obtained for the alloy
after its initial soaking at 1100°C/2 h and deformation in the temperature range of 1050÷950°C at strain rate 0.1 s-1. The increase of maximum yield stresses,
&#963;pp, and decrease of strain limit of the alloy, &#949;f, as the initial soaking temperature was rising up to 1150°C/2 h, with the strain rate increasing to 1.0 s-1, was
associated with a growth of the initial grain size and the degree of austenite saturation with alloying elements. The relationship between the maximum yield
stresses and the Zener-Hollomon parameter (Z) was described by &#963;pp = A × Zn power function. Activation energy for hot working (Q) was assessed for the
alloy after two variants of initial soaking, i.e. 1100°C/2 h and 1150°C/2 h and amounted, respectively, 442 kJ/mol and 519 kJ/mol.
Key words: A-286 superalloy, hot deformation, plastic properties, Zener-Holomon parameter, activation energy for hot working.1. INTRODUCTION
The behaviour of metals and alloys during hot plastic working has
a complex nature and it varies with the changing ...
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